This invention relates to power supplies and, more particularly, to circuitry for converting relatively low frequency low voltage AC power to high voltage DC power.
Many applications exist where a constant current high voltage source is desired. For example, present microwave oven power supplies utilize a ferroresonant 60 hertz transformer system. The output of the transformer is supplied to a half wave voltage doubler that converts this to a half cycle pulse suitable for powering a magnetron tube which generates power at microwave frequencies. A magnetron is a device that does not conduct current until the voltage applied thereto exceeds a threshold value. At this point, the magnetron conducts current which is limited only by its internal impedance. Presently used magnetron power supplies take advantage of the current limiting ability of the ferroresonant transformer to limit the magnetron current to a safe level. However, the voltage doubler in such systems is connected for half wave operation. In order to provide the desired average power, the system must deliver large amounts of power during the powered half cycle, resulting in a generally undesirable high peak to average power ratio.
It is therefore an object of the present invention to provide an improved high voltage DC power supply.
It is a further object of this invention to provide such a power supply with a reduced peak to average power ratio.
It is another object of this invention to provide a power supply protected from faults and overvoltages generated by transients and surges on the incoming commercial power line.
Similarly, arc discharge light producing systems, such as mercury vapor, fluorescent, high pressure sodium, etc., require high voltage current limited AC power to power their ballast systems.
It is therefore a still further object of this invention to provide an improved high voltage current limited AC power supply.